Selective party-line telephone system.



PATENTED JAN. 10, 1905.

A. J. SPRINGIBORN. SELECTIVE PARTY LINE TELEPHONE SYSTEM.

APPLICATION FILED APR.3,1903.

4 SHEETS-SHBBT 1 A TTORNE Y.

No 779,811. PATENTED JAN. 10, 1905.

x A. J. SPEINGBORN.

SELECTIVE PAR-TY LINE TELEPHONE SYSTEM.

APIiLIGATION FILED APR. a, 1903.

4 SHEETS-SHEET 2.

[35 ll 11f "i M 415 WITNESSES: c I S r 16. or w/NVENTOR.

No. 779,811. PATENTED JAN. 10, 1905. A. J. SPRINGBORN.

SELECTIVE PARTY LINE TELEPHONE SYSTEM.

APPLICATION FILED APR. s, 1903.

4 SHEETS-SHEET 4.

WITNESSES. WW CDZ ATTORNEY UNIT D STATES Patented January 10, 1905.

PAT NT OFFICE.

SELECTIVE PARTY-LINE TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 779,811., dated January10, 1905.

To atZZ whom it may concern/.-

Be it known that I, ALBERT J'. SPRINGBORN, acitizen'of the UnitedStates, residing at Cleveland, in the county of Guyahoga and State ofOhio, have invented a new and useful Improvement in Selective Party-LineTelephone Systems, of which the following is a specification.

This invention relates to partyline telephone systems, and is animprovement on the system shown and described in my pending applicationfor patent, Serial No. 64,302, filed June 12, 1901.

The objects of said improvements are to render said system moreautomatic in its operation and to make the apparatus simpler in itsconstruction and electrical connections. These objects I attain in thesystem illustrated in the accompanying drawings, in which Figure 1 is adiagrammatic view of two partylines, each being provided with twosubstations and each extending to the central station, the connectionsand apparatus in which are shown. Fig. 2 is a diagrammatic view of aparty-line which is provided with four telephones or substations inparallel, showing the dials for the selecting devices. Fig. 3 is a viewof the clockwork for operating the selecting devices at both the centraland substations, the same being taken on line 3 3 of Fig. 4. Fig. 4 is acentral sectional view through either dial A or B of Fig. 2, taken online 4 4 of said figure, but showing the clockwork mechanism of Fig. 3in plan with the same released by its electromagnet. Fig. 5 is a detailview of a portion of the apparatus shown in Fig. 4, showing the parts ina different position. Fig. 6 is a perspective view of a selector-key anda portion of the spring-connecting finger that cooperates with it. Fig.7 is a view taken on the line 7 7 oi'Fig. 5, showing the beveled head onthe dial-hand keys. Fig. 8 is an enlarged diagrammatic view of theconnections at the substations. Figs. 9, 9, and 10 are perspective viewsof portions of the substation selecting apparatus, showing the lockingdevices for the keys and telephone-hook. Fig. 11 is adetail view ofaportion of the rod leading to the telephone-hook, showing theexpansible and compressible portion of the same. Fig.11 is a detail viewof the Zero-key. Fig.

12 is an enlarged front view of the central selecting device and itselectrical connections. Fig. 13 is a side view of the selecting deviceshown in Fig. 12. Fig. 14 is asectional view of the same, taken on line14 14 of Fig. 12. Figs. 15, 16, and 17 are detail views of portions ofthe central selecting apparatus, and Fig. 18 is a general View of atelephone having a selecting device attached thereto.

In the telephone system herein described I have sought to make theoperation entirely automatic and to relieve the operator at the centralstation of as much labor as possible.

In the drawings, in which similar reference characters designatecorresponding parts throughout the several views, 1 and 2 represent themain wires of party-line telephones, one set of said wires in Fig. 1being connected with substations A and B and another set being connectedwith substations C and D. All of said sets of wires lead to aswitchboard 3 at the central station, which board is shown divided, soas to more clearly illustrate the electrical connections.

In each of the telephones shown, 4 designates the hook, upon which thereceiver 5 is adapted to hang in the usual manner. 6 is the transmitter,the circuit from which leads through the primary of the induction-coil7. 8 designates the call-bell, which is preferably of the ordinarymake-and-break-circuit form. At the central station, 9 represents theordinary jacks ot' the switchboard, and 10 the plugs for the same.

This system depends for its operation upon a series of selectingdevices, one for each substation, and also upon one or more of asomewhat different form of selecting device at the central station. Inorder for these devices to always select the particular party with whomconnection is desired to the exclusion of all other parties on the line,it is necessary for them to move synchronously. To accomplish thisresult, I provide each selecting device with clockwork mechanism, whichis shown in detail in Figs. 3 and 4, the said clockwork being identicalin both the central and sub stations. While this mechanism may be of anysuitable character, as shown in the above mentioned figures, 1t consistsoi a drum-arbor 11 and drum 12, within which is coiled the spring 13. Aswill be understood, one end of this spring is fastened to the drum,while the other end is attached to the drumarbor. Secured to the drum isa large pinion 14:, which meshes with and drives a small pinion 15,which is secured to the central shaft 16. Also secured to the centralshaftis a large pinion 17, which meshes with a small pinion 18 on theshaft 19, which carries a governing-fan 20. Instead of a fan a suitableform of escapement mechanism may be employed, if desired. Projectingfrom the frame of the clockwork mechanism are studs 21 and 22, uponwhich are journaled gearwheels 23 and 24, which are geared toa smallpinion 25 upon the drum-arbor. Also journaled upon the stud 22 is alever 26, which carries a pawl 27 for engaging with the teeth of thegear-wl1eel 24 to drive the same when the lever is moved forward againstthe tension of its spring 28. For preventing the backward rotation ofthe gear-wheel 24 I provide a detent-pawl 29, which is secured to astationary part of the framework and engages with the top teeth of thegear-wheel. From this description it will be understood that when thelever 26 is moved forwardly it will turn the gear-wheel 2a and throughthe train of gearing will turn the drum-arbor to wind the spring 13.Furthermore, when the central shaft is permitted to turn by releasingmechanism presently described the train of gearing extending from thedrum-arbor to the governing-fan will be rotated. This releasingmechanism consists of a notched disk 30, which is secured to the centralshaft, in the notches of which the beveled end of a lever 31 is normallypressed by means of a spring 32. hen this lever is moved so as todisengage its beveled end from the notches, the clockwork mechanism isfree to operate.

It will be seen that it is necessary to release all of the mechanisms onthe various substations on a line at the same instant, and for thispurpose I provide each of the selecting devices with an electromagnet33, which is preferably mounted between the ends of the levers 26 and31, so that when a current is passed about the same these levers will bedrawn toward each other to release the clockwork and also to wind up thespring. The gears for winding the spring and those for driving thecentral shaft are so proportioned that the spring is always kept underdriving tension.

The frame for the clockwork mechanism is secured to the rear side of aninner dial-plate 34, and the central shaft projects through the same andalso through the center of the outer dial-plate 35, the frame and theinner dial being secured together by the posts 36 and the dials beingconnected by similar posts 37, and the outer rim 38 of the selectingdevice. About midway between the outer and inner dials and paralleltherewith is a disk 39, of insulating material, to the inner surface ofwhich are secured conducting-rings 40, that are placed concentric withthemselves and with the shaft 16. Attached to the back side of the disk89 and radiating from points near the central shaft are spring arms 41.These arms extend through slots 12 in the outer rim 38. and just beyondsaid rim they are bent forwardly at 43, so as to bring their free endsalmost flush with the outer dial 35, when the arms are permitted toassume their normal position, as shown in Fig. 4. Secured to the frontsides of these spring-arms are contact-springs H, which are adapted tobridge across and shortcircuit the conducting-rings 40 when the arms arein normal position, but which are lifted outof contact when the arms aredepressed, as shown in Fig. 5. The rings 10 and the contact-springs 1 iform under conditions presently set forth parts of an electric circuitthrough which a current flows to set all the selecting devices at thesubstations to the desired point for unlocking the telephone at theparticular substation desired, while all the other telephones aremaintained in locked condition. For depressing the spring-arms andbreaking the contact at the rings 40. I provide the central shaft 16with a dial-hand 45, which turns about over the outer dial andterminates in an antifriction-roller4:6. This roller moves in an orbitover the free ends of the springarms ll and depresses them, so as tobreak the contact between the springs 41 i and rings 1O, as shown inFig. 5. When the contact is thus broken at the substation that iscalling and that controls for the time being the party-line, all theselecting devices stop with the dial-hands pointing toward the sameindicating-letter. By reference to Fig. 2 it will be seen that while allthe dials have the same arrangement of letters'there is a differentarrangement of keys 47, which keys are adapted, when depressed by thedial-hand, as hereinafter described, to close a bell-circuit forsounding a call-bell 8. There is one of these keys at? for each of thespring-arms 4:1, and they are arranged in pairs, so that when thedial-hand moves around to break the contact at the rings 40 in onestation it will simultaneously depress a key 4L7 and close thebell-circuit at that station. As seen in Fig. 2, but one dial has a keyatA, but one has a key at B, but one has a key at (J, and but one has akey at D, so that normally when one telephone on a line is in use noother telephone on that line will be called. One of the keys 47 is shownin enlarged views in Figs. 4, 5, 7, and 9, from which it will be seenthat it is provided with an enlarged head that projects beyond the faceof the dial 35 and that is beveled so that a roller 48, that iscarriedby the dial-hand, may more easily depress it. The keys are normallypressed outwardly by springs 19, that are coiled about their shanks andare preferably guided at their inner ends cuit.

in bosses 50, that project from the outer face of the disks 39. Mountedon said disks on the opposite side from the conducting-rings 40 andpreferably concentric with the shaft 16 are a second pair ofconducting-rings or segments of rings 51, said rings being clearly shownin Fig. 8. The bosses and keys 47 are placed between these segmentalrings. Opposite each of the said bosses spring-contacts 52 are connectedwith the segmental rings and are passed through the disks 39 and thenbent down into the bores through the bosses. When the keys 47 are intheir outer position, as shown in Fig. 4, the contacts-are separated;but when they are pushed in, as shown in Fig. 5, they will be forcedbetween the contacts and will complete the bell-circuit. As willhereinafter more clearly appear, a plurality of separate contact-pointswith independent conducting-wires may be employed instead of theconducting-rings 40 and the segmental conducting-rings 51. From thisdescription it will be clear that when the dialhand depresses aspring-arm 41 it will break the contact at rings 40 and at substantiallythe same instant will close the contacts at the corresponding key 47.

In the system described in my former application above referred to theparty who should take down the receiver and ask the centralop- 'eratorfor connections with another party was obliged to give his own letterand wait for central to place his own phone in the talking-cir- For thepurpose of relieving both the party calling and the central operator ofthis trouble I have the spring-arms 41 at the single letters A, B, C,and D in such position that the springs 44 are normally in contact withthe conductingrings, as seen in Fig. 10. w The said rings are in acircuit that is controlled by the telephone-hook, and when the receiveris up the circuit is broken; but as soon as A, for example, takes downhis receiver to call he completes the circuit and a local battery startsall the telephone-selectors on his line, which selectors continue tooperate until As dial-hand reaches A on hisdial, when the spring-arm 41is depressed and the circuit broken. Each party calling therefore placeshis own line in the proper condition, and thus relieves the centraloperator of that operation. Vhen As dial-hand stopped at A, it depressedthe key 47 at that letter, and thus closed the bell-circuit there. Thiscircuit, however, is controlled by the telephone-hook, and when thereceiver is down the circuit is broken, so that As bell is not sounded.

It may sometimes happen that two parties on the same line wish toconverse. Suppose, for example, that A should want to call D. If heshould proceed in the usual way, it is evident that the dial-hands wouldbe stopped at A and that D would not be placed in connection. To providefor such conditions, I

place contact-arms 41 at points on the dials which are designatec AB,AC, AD, &c., as shown in Fig. 2, and arrange radial keys 520 tocooperate with said arms. The resiliency of these arms tends to makethem assume the position shown in Fig. 4; but they are normally heldback by the keys, as shown in Fig. 5, said figures showing the AB key.As appears from Fig. 6, the forwardly-bent portion 43 of thesespring-arms is provided with a slot that has a narrow part 53 and a widepart 54. The keys 520 are provided intermediate their length withenlarged rectangular portions 55, that normally rest in the wide part ofthe slots in the arms, as shown in Fig. 5, at which time the arms aredepressed. The keys are supported partly by the outer rim 38 and partlyby the annular flange 56, that surrounds the selecting device, and theyare normally held outwardly by springs 57, that are coiled about theirshanks. With this description it will be understood that when A wants totalk with B he simply pushes in the AB key a distance sufficient tobring the enlargement out of the wide part 54 of the notch in thespring-arm, when the latter moves forwardly to close the contact withthe rings 40. Then when he takes his receiver off the hook the selectingdevices start forward and continue untilAs dial-hand depresses thespring-arm and breaks the contact again. When the arm moved forwardly asabove described, the shank of the key 520 entered the part 53 of thenotch and the en- 'largement 55 prevented the outward movement of thekey until the spring-arm was again depressed so as to bring the widepart of the notch opposite the key, when the latter was free to snapoutwardly to hold the arm in its depressed position. In moving to the ABkey the dial-hand passed and depressed the spring-arm at A. This armhaving no key 520 to detain it would, if permitted, spring back as soonas the dial-hand had passed and bridge the contact-rings at A, with theresult that the dial-hand will not stop at AB. In order to hold the Aspring-arm depressed, I provide a locking-hook 58 (see Fig. 10) with abeveled face that is cammed back as thearm 41 is depressed and thatmoves forward again as soon as the arm has passed it, the hook engagingwith the front of the arm to hold it back. This hook is carried on theend of an arm 59, that is journaled on the central shaft 16, and it isheld in its engaging position by means of a coiled spring 60, that issecured at one end to a stationary part of the mechanism'and engages thearm 59 with its free end. Normally thedial-hands all stand at O, whichin this case I prefer to place at the left part of the dials. The linesare automatically restored to their Zero positions when the parties whohave been talking hang up their receivers. It thus becomes necessary tohave a restoring-circuit in each line that is closed when the receiveris hung up and that continues unbroken until the dial-hands reach zero.The particular circuit for accomplishing this result will not be traceduntil the various mechanisms have been described; but it has one pair ofcontacts under the receiver-hook and another pair at the zero-key, whichkey is shown at 61 and is designated 0. The outer conducting-ring 40 isfor convenience used for one contact of the latter pair, and the othercontact is shown at 62. (See Figs. 4:, 8, and 10.) The zero-key, likethe bell-circuit keys 47, is provided with a beveled head, so that itcan be easily depressed by the roller 48 on the dial-hand. For a purposehereinafter made to appear the zero-keys are of a double structure,consisting of an outer sleeve 63 and an inner plunger 64, that extendsbeyond the sleeve at each of its ends. The outer end carries the beveledhead heretofore referred to, and the inner end is provided with a cam65, that is adapted to engage the arm 59 as the plunger is depressed bythe dial-hand to push back the hook 58, and thus release the springarm41, that may be retained thereby. Intermediate the cam 65 and the headthe plunger has a cam 66, that projects through a slot 67 in the sleeve,said cam preferably resting against the outer dial 35 when the plungeris in its outer position. Between the cam 66 and the upper end of thebore in the sleeve is a spring 68, that presses the plunger outwardlyexcept when it is restrained by the dial-hand. The lower end of thesleeve is provided with a plate 69, between which and the dial 35 is acoiled spring 70, that pushes out the sleeve when it is released.Projecting from the inner end of the sleeve 63 is a stud 71, to which issecured a contact-spring 72, that is adapted, when the sleeve andplunger are released, to bridge the contacts i0 and 62 for restoring theselecting devices on the line to zero position. It will be evident thatif the sleeve 63 were permitted to spring out on all the telephones on aparty-line as soon as the dial-hand moved away from zero position thecontacts 4:0 and 62 would be closed on those selecting devices belongingto the telephones with their receivers up, with the result that thereturn-to-Zero circuit would be fully established in those telephonesand the dial-hands could not stop until they had again reached Zero. Thesleeves, therefore, are prevented from moving outwardly at thetelephones unless the receiverhooks are elevated. This is accomplishedby extending a rod 73 from a short arm 7% of the receiver-hook t back tothe zero-key to intercept the sleeve and prevent its outward movement.This rod terminates in an angular plate 75, said plate normallyextending in front of an angular pin or finger 76 on the sleeve, asshown in Figs. 4c and 10. When the receiver-hook is up, the plate 75 isdrawn away from the pin 76, and when the dial-hand moves away from Zerothe sleeve and plunger will assume their outward positions, bringing thepin 76 in front of the edge of the plate 75. Then when the receiver isagain hung up the plate abuts the angular pin and would prevent thedepression of the hook, which is necessary for completing thereturnto-zero circuit, were it not for the telescopic structure shown indetail in Fig. 11. The plate 7 5 is attached to a small cylinder 77, inwhich works a piston-head 78, that is formed on the end of the rod 73.Between the cylinder and the piston-head is a compressible spring 79.This structure permits the hook to be depressed to close thecontact-points of the return-to-zero circuit, and when the dial-handpushes in the ZBIO' key the spring 79 causes the plate 75 to snap infront of the angular pin 76. As the dial hand will be stopped by thereleasing-lever 31 the instant the current is broken, so that it willnot be able to further depress the sleeve 63, it will be seen that thecontact plate 72 will be lifted from the contacts 410 and 62 such anexceedingly short distance that changes of temperature or slight jarswould be sufficient to cause trouble. To still further depress thesleeve and separate the contacts, I form the front part of the plate 75with a cam edge 80, that forces the sleeve inwardly as the plate movesforward under the impulse of the spring 79.

In the operation of any system it is necessary that when the lines arenot in use and the dial-hands stand at Zero all the receiverhooks andall the keys 520 be unlocked, and it is also necessary to lock the hooksand keys as soon as the dial-hands move from Zero, after which neitherwill be unlocked unless the dial-hand stops on a key 47 of someselector, when the hook and keys for that seletor will be released. Ofcourse all keys 520 and receiver-hooks will be released when thedial-hands return to zero. To accomplish these results, I form a head orbutton 81 on the rods 73 at a point a short distance inside the outerrim 38 when the hooks are down, said rods passing through said rim. Ialso form similar heads or buttons 82 on the inner ends of the radialkeys 520, said heads being in an opening in the rim 38 when the keys arein their outer positions. Mounted to turn about the central shaft and tomove in close' proximity to the inner surface of the outer rim is alocking-ring 83, said ring being preferably carried by radial arms 84,that are journaled on the central shaft. Aspring 85, that is coiledabout the shaft, has one end secured to a stationary part of the deviceand has its other end bearing against one of the arms 84 to hold thelocking-ring in normal position. (See Fig. 10.) The locking-rings areprovided at points opposite the rods 73 and the keys 520 with holes 86,(shown most clearly in Fig. 9,)said holes having narrower slots 87connected therewith. The holes 86 are of substantially the same size asthe heads 81 and 82, and when they are in normal position they aredirectly opposite said heads, so that the head 81 may pass through thehole, moving outwardly, or the heads 82 may pass through movinginwardly. The cam 66 on the plunger of the Zero-key shifts the ring tothis position when it is depressed by the dial-hand, as is shown in Fig.10, where the cam is seen engaging with one of the arms 84, that carrythe ring. When, however, the dial-hand moves away from Zero, the plungerand cam move outwardly and the spring causes the ring to shift, so as tobring the neck 88 (see Fig. 11) of the rod 73 into the narrower slots 87in the ring and the heads 82 of the keys opposite said slots. This beingthe position of these parts, it is obvious that the telephone-hookcannot rise or the keys be depressed. By reference to Fig. 9 it will be'seen that all the bell-circuit keys 47 are provided with aring-shifting cam89, that pushes back the arms 84 and unlocks thereceiver and keys on the telephones. When, therefore, a dial-hand comesto rest on a key 47 and the hook for that telephone is down, the bellwill be sounded and the locking-ring shifted so that the hook will beunlocked.

By reference to Fig. 2 it will be clear that if D, for example, iscalled and the dial-hands all start around for D one of the otherparties on the line, as B, seeing the hand moving could take down hisreceiver. Then when his dialhand reached his key 47 his ring 83 would beshifted and his telephone-hook would fly up and place his telephone inthe talking-circuit. Before explaining my means for avoiding this resultI will call attention to the fact that the dial-hands are controlled bythe electromagnets 33 and that they can move only as said magnets areenergized. I therefore operate a second locking-ring by means of thesemagnets, said ring being mounted to turn just inside the ring 83 andhaving holes 91 with narrow extensions 92, that normally register withthe holes 86 and extensions 87. The ring 90 is supported on arms 93,(see Fig. 9,) that are journaled on the central shaft 16. Secured to oneof these arms and to the releasing-lever 31 (see also Fig. 3) is a linkor rod 94, said rod connecting the arm and lever rigidly, so that theymove together. The leverspring 32 holds the ring with its holes inunlocking position when the magnet is deenergized; but when the latteris energized the inner ring 90 will be shifted to lock thereceiver-hooks down and the keys 520 outv It will thus be seen thatafter the dial-hands move from zero position it is impossible to releaseany hook or depress any key until the hands come to rest on a key 47,when the currents through the magnets are broken and the ring 90 comesto its unlocking position. The depression of that key 47 also shifts thering that causes all the dial-hands on that line to be returned to Zeroposition.

The selecting device at the central station is similar in many respectsto those at the substations. It has an outer dial 95. upon which are theletters A, B, C, D, &c., and over the face of which turns the dialhand96. This dial-hand has a roller 97 corresponding with the roller 46 onthe other dial-hands for pressing down the spring-arms 98 opposite thesingle letters on the dial and the special springarm 99 at the zeroposition, which in this device is preferably at the lower part of thedial. Precisely the same form of clockwork mechanism is employed as thatpreviously described, so that illustration and description of the sameis deemed unnecessary. Mounted on the inner face of the outer dial are apair of conducting-rings 100, which are bridged under conditionspresently set forth by spring contact-plates 101, that correspond withthe plates 44, heretofore described. The outer rim 38 is surrounded byone of the flanges 56, and in this rim and flange are guided radial keys102, which are like the keys520, except they have no head or button 82,there being no locking-rings in this selector. As in the other selectingdevices, the spring-arms have a forwardlybent portion in which are theslots for co6pcrating with the squared portion 55 of the keys. Theoperation of a key 102 releases the corresponding spring-arm 98, whichsnaps forward and closes the circuit between the conducting-rings 100.The special arm 99 (see Figs. 16 and 17) is provided with a forwardprojection 103, upon which the roller'97 of the dial-hand 96 rests whenit is in its zero position, at which time its spring-plate 101 is out ofcontact with the conducting-rings. The arm 99 is extended beyond theprojection 103, and on its extreme outer end it has a linger 104 pivotedthereto. A flange 105 just inside the finger prevents an inward movementbeyond the position shown, while the finger can be readily depressed, asindicated in dotted lines. A spring 106 tends to hold the finger in itsinner position.

The central selecting device is in my improved system mounted upon theupper end of a hollow standard 107, that is pivoted to a rod 108,preferably below a table or board 109, through which the standardprojects,

and through a slot 110, in which it can swing back and forth, asindicated in dotted lines in Fig. 12. Below the pivot the standard ispreferably flattened and is of a shape resem- 83 for that selectingdevice; but as there is no 1 bling somewhat an inverted cross having thelower depending part 111 and the outstretched arms 112. 113 is asolenoid through which extends a plunger 114, the upper end of which iswedge-shaped. The lower end of the depending part 111 is formed on anarc concentric with the pivot 108, and near each of its outer edges itis provided with notches 115,

' into which the end of the plunger 114 engages when the standard 107 isswung, so that the latter will be temporarily held against return. Aspring 114 normally holds the plunger retracted. A pin 116, covered withinsulating material, as indicated at 117, projects from the face of thedepending part of the standard between fixedly-mounted ducting-springs118, (see Fig. 5,) said springs returning the standard to and holding itin vertical position when it is released by the plunger. These springare mounted upon bars 119 and are insulated from one another, the barsbeing preferably formed of insulating material. They and the rod 108will also preferably be made of considerable length, so as toaccommodate a series of selecting devices arranged in alinement. Theconstruction and connections will be the same in all selecting devices,however, so that such a series is not illustrated.

120 is a stationary arm that is mounted upon the table 109 opposite theslot 110, the same extending upwardly to a point almost opposite thehinged finger 104 of the arm 99, where it is provided with a cam-fl ange121, said flange being curved so as to be coaxial with the rod 108. Atthe center of the flange is a notch 122, into which the finger 104projects when the standard is in vertical position and the dial-hand isreturned to zero. \Nhen the selecting device is swung to either side,the finger moves opposite the flange 121, which prevents the arm frommoving forwardly to bridge the conducting-rings 100. In order to permitthe same to move, however, it is only necessary to depress the end ofthe finger 104 below the plane of the fiange,when contact will be made.

123, Fig. 12, is a solenoid into which extends a plunger 124. Thisplunger carries at its end opposite the solenoid a spring contact-plate125, that is adapted to bridge across the space between the wires 126and 127 and connect them electrically when the solenoid is energized.The plunger also carries beside its armature 128 a plate 129, to theends of which are secured blocks of insulating material, as shown.Pressing against these blocks and normally retracting the plunger arespringcontacts 130, which are secured to stationary parts of theapparatus and which are adapted to be pressed against stationarycontacts 131 when the plunger is drawn baclr by the solenoid.

The outer ends of the arms 112 of the standard 107 are each providedwith a pair of contact-points 132 and 133, which when the standard ismoved are adapted to contact with a pair of stationary contacts 134 and135, respectively. The lower end of the standard is provided withcontacts 136, 137, 138, and 139, which when the standard is in avertical position contact with stationary points 140, 141,

142, and 143, respectively.

144 is a battery or other source of electric:

power at the central station that furnishes the necessary current forsetting the lines in condition. Connected with the positive side of thebattery is a wire 145, that is passed up the hollow of the standard 107,so as to control an electromagnet. (Not shown, but just like the magnets33, illustrated in Figs. 3, 4, and 9.) Below this magnet on thereturn-circuit I shall designate the wire 146. At its lower end it isconnected to the middle of a wire 147, that is carried by the arms 112,and terminates at each end in a contact-point 132. The wire 126, abovereferred to, is connected with wire 146 just opposite the rod 108.

148 and 149 are the conductors in the cables that lead to the plugs 10,(see Fig. 1,) and these conductors are connected to the spring-contacts118. (See Fig. 15.) They are also connected with the contact-points 134and 135, respectively. The spring-contacts 130 are connected with theconductors 148 and 149, and

saidconductors are short-circuited through 9 them when the solenoid 123is energized. This solenoid is connected through a resistance 150 withthe conductor 149 and through another resistance 151 and wire 152 withthe terminal 140, which is normally in contact with 136, The contact 136is connected with contact 139 by means of a wire 153, that is carried bythe lower part of the standard 107, The contact 139 normally haselectrical connection with the terminal 143,and this is connected,through the wire 154, with the conductor 148. From this it will be seenthat when the standard is in a vertical position the conductors 148 and149 are connected through the solenoid 123 and resistances 150 and 151.The wire 127 is connected with the contact 141, and the contacts 137 and138 are connected bya wire 155. The contacts 133 are connected by a wire156, and with this wire is connected a wire 157, that leads to thesolenoid 113. Beyond this solenoid I shall designate this wire 158, saidwire leading to the negative side of the battery 144. The wire 158 isalso connected with the contact-point 142.

.I. will now direct attention to Figs. 1 and 8, while describing theconnections at the substations. 159 is the talking-battery, which isconnected through the wire 160, transmitter 6, the induction-coil 7, andwire 161 with a terminal point 162 above the receiver-hook 4. 163 isanother terminal point above the hook, said point being connected withthe talkingbattery through the wire 164. As will be understood, when thehook is raised the termi nal points will be connected therethrough andance 196, with the wire 167.

a current will flow. Instead of supplying the current from a localbattery I may employ the well-known central-energy system, if preferred.The impulses that are'set up in the induction-coil are transmittedthrough the receiver 5 and wires and 166 to the main wire 2 of theparty-line, which leads to the jack in the switchboard. pass through thewires 148 to the wire 2 of the other line, which conducts them to thesubstation that is in the circuit. From said station they are returnedthrough wires 167, 1, 149, 1, and 167 to the receiver-hook 4 and fromthence through the hook and wire 161 to the induction-coil again. seenthat there is nothing novel about the talking-circuits.

The bell 8 is placed in parallel with an electric motor 168, whichdrives a make and break circuit device 169, consisting of a disk ofinsulating material upon which brushes 169 and 170 bear.

171 is a strip of conducting material on the disk that connects thebrushes electrically for a short time at each rotation of the disk. Itwill be remembered from the previous description that there are two setsof contactpoints in the bell-circuit that must be simultaneously closedbefore the bell can ring. One of these sets is the segmental rings 51 inthe selecting device, and the other setis shown at 172 and 173 under thereceiver hook. \Vhen the hook is down, the contact 172 is pressed intoengagement with the contact 173, as shown.

174 is a local battery that is connected with contact-point 173 throughthe wire 175. The contact 172 is connected with the return-tozerocontact 62 through the wire 176. Leading from this wire is thebell-circuit Wire 177, said circuit, dividing at 178, part of thecurrent going through the bell and brushes 169 and 170 and the rest ofit through the motor, the two currents uniting at 179. Beyond this pointa wire leads to the outer segmental ring 51. The inner ring isconnected, through the wire 181, with a wire 182, that leads to thebattery 174. This latter wire is also connected with the wire 167,thatleads to that substation.

Branching off from the wire 175 and leading to a terminal point 183above the hook is a wire 184, and a similarly-located terminal 185 isconnected by a wire 186 with the inner conducting-ring 40. The outerconducting-ring is connected with the wire 166 through the wires 187,188, and 189 and the relay 190. The wire 189 is connected with a pivotedarm 191, an end of which constitutes an armature for the relay 190 andthe other end of which forms a terminal that when the relay isdeenergized contacts at 192 with the wire 193, that leads to anotherrelay, 194. This relay is connected, through the wire and resist- Thewires 187 From there they It will thus be and 193 are connected througha resistance 197. The relay 194 controls a pivoted arm 198, similar tothe arm 191, to make and break a current through the electromagnet 33from the local battery 199. This current flows from the battery througha wire 200, magnet 33, wire 201, pivoted arm 198, and wire 202 back tothe battery.

When users of. telephones in calling do not receive a prompt answer fromthe central station, they are prone to pump the hook up and down toattract the attention of the operator. This would naturally close thecontacts 172- and 173 below the hook and would, as will hereinafter morefully appear, establish the return-to-Zero circuit. 1 To keep thesecontacts apart at this time when the receiver is down, I pivot a smallbell-crank 203 to the casing below the hook in such a manner that thereceiver will when hanging from the hook depress its lower end againstthe tension of a spring 204. To the upper end of the bellcrank I pivot aplate 205, of insulating material, said plate being so placed as toslide between the contacts 172 and 173 when the receiver. is removed. Itwill therefore be impossible to close these contacts unless thebellcrank 203 is depressed, and the hook can be pumped as much as may bedeemed necessary without disturbing the selecting devices on the line.

206 is a signaling device at the central station, one of said devicesbeing connected with each jack in the usual way to indicate to theoperator when a line is calling.

In describing the operation of my system 1 will first assume that A onone-party-line desires to talk'with D on another line (see Fig. 1) andthat D answers his call. All the dial- .hands are at their Zeropositions when A takes his receiver off his hook 4, and allreceiverhooks being unlocked the hook flies up to close the contacts162, 163, 183, and 185. It being remembered that the conducting-rings40, Figs. 8 and 10, are bridged at A on As selecting device, a currentis permitted to flow from the battery 174 at As telephone through thefollowing circuit: wires 175 and 184, hook 4, wire 186, inner ring 40,contactstrip 44, and outer ring 40, beyond which it divides, part of itflowing through the wire 187, relay 190, wires 188, 189, and 166 to themain line 2, which leads to the jack on the central switchboard, throughthe signaling device 206, the main line 1, back to the substation A, thewires 167 and 182 to the battery again, and the other part flowingthrough the resistance 197, relay 194, wire 195, resistance 196,'andwires 167 and 182 to the battery. The first branch of this circuit tothe the electromagnet 33.

IIO

be remembered, releases the clockwork mechanism and winds up the same,so that the dialhand 45 starts from Zero position and travels arounduntil it reaches A, when it depresses the spring-arm 41 and breaks theconnection between the conducting-rings 40. The current in the circuitabove traced is broken, therefore, and the relay 194 being deenergizedthe current through the magnet 33 is also broken, and the locking-lever31 stops the clockworkmechanism. It is not all of the current thatpasses out to wire 166, as above described, that goes to the signalingdevice 206, since it is this current that must control the otherselecting devices on the line with A, so as to lock them out of thetalking-circuit. Since the connections are the same in all thesubstations, I will trace this current through the one shown in Fig. 8,into which it will flow over the line 166. The receiver-hook being down,as shown, the current is compelled to flow through wire 189, contacts191 and 192, wire 193, relay 194, wire 195, resistance 196, and wire 167to wire 1, and thence back through the circuit already traced to Asbattery. The relay 194 closes the local circuit for releasing thedial-hand, and said hand will turn, as above described, as long as thecurrent flows from substation A, said current being broken when thehands reach A on the dials. Originally all the receiver-hooks and allthe keys 520 were unlocked. WVhen A lifted his receiver, the button orhead 81 on the rod 73, that is connected with his hook, passed beyondthe locking-rings 83 and 90, and the plate 75 permitted the zero-key tomove outwardly, so as to bridge the contacts 40 and 62 to return theline to zero when A hangs up his receiver. On the other telephones onthe line the movement of the dial-hands from Zero permitted the plunger64 of the zero-key to move outwardly, so that the locking-rings 83 couldshift to lock the telephone-rods and all the keys 520.

I will now describe the operation of signaling D and of placing him inconnection with A. When the operator at the central station notices thesignal 206, she inserts the plug 10 into the jack 9 in the usual mannerand ascertains that A is desiring connection with D on another line. Sheaccordingly depresses the D pin on the central selecting device, whichreleases the spring-arm 98 at that point and connects theconducting-rings 100, and then she inserts the other plug 10 on the samecable into Ds jack 9. She then swings the standard 107 toward Ds jack,(the right in Fig. 1,) when a current will be established that flowsfrom battery 144 through the following circuit: line 145, ring 100,contact-plate 101 at the D position, other ring 100, wires 146 and 147,contacts 132 and 134, wire 148 to plug and jack, wires 2, 166,189, and193, re-

lay 194, wire 195, resistance 196, wires 167 and 1 to the jack and plug,wire 149, contacts 135 and 133, wires 156 and 157 to the solenoid 113,and wire 158 to the battery again. This current controls the operationof the dial-hand 96 on the central selecting device and also the relays194 for establishing the local circuits for operating the substationdial-hands, and as soon as the hand 96 reaches the D position itdepresses the arm 98 and breaks the circuit, so that all the devices onDs line are stopped with the hands at D. Now it will be remembered thatno party on that line has a bell-circuit key 47 at this point except Dand that the rings 83 on the other selecting devices will have thetelephone-hooks and keys 520 locked, so that D cannot be disturbed. Ashas been stated, B or C, for example, could have removed their receiverswhen the dial-hands started and secured the release of theirreceiver-hooks as their dial-hands passed their keys 47 if it had notbeen for the rings 90, which are shifted to locking position by themagnets 33 and are held in that position as long as the current flows.When the standard 107 was swung to establish the above-describedcircuit, the pin 116 separated the spring-contacts 118, Fig. 15, so thatthe current could not flow back and disturb As line, and the standardwas held in this position by the plunger 114, which was drawn into thenotches 115 by the solenoid 113. hen the current is broken, however, theplunger disengages the notches, and the standard is returned by thecontacts 118, which close together below the pin 116. A is now intalking-circuit with D and all other parties are locked off of thelines; but D has not yet been signaled. The depression of his key 47closed the contacts 52 of his bell-circuit, however, andhistelephone-hook being down a circuit is established at his substationthrough the following connections: from battery 174, wire 175, contacts173 and 172, wires 176 177, hell 8, brushes 170 and 169, wire 180, outersegmental ring 51, contacts 52 and key 47, and wires 181 and 182 to thebattery. As before described, the bell is caused to ring intermittentlyby the motor 168 and disk 169, and this ringing is kept up until Dremoves his receiver from the hook 4. Of course the bell could be givena continuous ring, if preferred, in which case the circuit between thepoints 178 and 179 through the motor would be omitted. It will beremembered that the bell-circuit key 47 is provided with a cam 89, thatshifts the locking-ring 83 when it is depressed by the dial-hand, sothat Ds receiver-hook is unlocked.

It is desirable that each party reestablish his own line to the Zeroposition when he is through talking. It being remembered that thetelephones that have been in use have their zero-keys released and thecontacts at 40 and 62 closed, the depression of their hooks by theirreceivers closes the contacts 172 and 173, and a return-to-Zero circuitis established through the following connections: wire 175,

contacts 172 and 173, wire 176, contacts 62 and 40, wire 187, relay 190,wires 188, 189, 166, and 2 to the Wires 166 of the other substations onthe line, from 166 in said substations through wires 189 and 193, relay194, wire 195,resistance 196. wires 167 and 1 to .the wire 167 of thetelephone that has been in use and then through wire 182 to the battery174. At the outer ring the current divides, as previously described, andflowing through the resistance 197, relay 194, wire 195, and resistance196 to the wires. 167 and 182 closes the local circuit from the battery199 to return the selecting device to Zero. It will be understood thatthe current through the relays 194 at the other substation close theirlocal circuits and set them to zero. When the dial-hands reach Zero, thekeys at that point are depressed and the circuit is broken, so that alldial-hands come to rest. Simultaneously the rings 83 and 90 are shiftedto unlock all the hooks and keys 520.

In the case above selected, in which A was talking with D, thedial-hands on Ds line, having a shorter distance to travel, will reachzero sooner than those on As line, and as a result the current from Asline might disturb the substations on Ds line.

To prevent this result, I short-circuit the conductors 148 and 149 atthe central station through the following connections: wire 154,contacts 143 and 139, wire 153, contacts 136 and 140, wire 152,resistance 151, solenoid 123, and resistance 150. A suflicient amount ofcurrent will flow through this circuit to cause the solenoid to closethe contacts 130 and 131, which will establish a circuit between theconductors that cuts out the resistance 150 and 151. This short circuitwill carry practically all the current and prevent it from flowingthrough central to the other line to disturb the selecting devicesthere. Inasmuch as this short circuit is at the central station, whereit is removed as far as possible from the substation, resistance of themain wires leading to the central station will ordinarily be sufiicientto force the currents through the local circuits at the substations of asufficient strength to operate the delicately-poised circuit-closersthere. If, however, it should be found that the current flows too freelythrough this short circuit, more resistance will be placed therein, thisshort circuit being merely intended to keep a current from passing tothe other line of suflicient strength to disturb the selecting devicesthereon.

As was previously stated, when the circuit was broken in the centralselecting device the standard 107, carrying the said device, returned toits vertical position. As the clock- Work mechanism in this device isthe same as that at the substations, the dial-hand 96 must have beenstopped at D. WVhile mechanical means could easily be adapted to returnthis hand to zero, I prefer to have this done automatically, however,when the lines are being reset, and for this purpose I provide thesolenoid-plunger 124 with the contactpiece 125, which is adapted toconnect the wires 126 and 127. When, therefore, A and D hang up theirreceivers, the return-to-zero currents energize the solenoid 123 anddraw the contact-piece into position to bridge across the wires 126 and127, so that a current can flow from battery 144 through the followingconnections: wire 145 to the central selecting device, where it releasesthe clockwork mechanism, as in the other devices, wires. 146 126,contact-piece 125, wire 127, contacts 141 and 137, wire 155, contacts138 and 142, and wire 158 to the battery. The dial-hand 96 presses backthe special spring-arm 99 (see Fig. 17) when it reaches the Zeroposition and breaks the connection between the conducting-rings 100. sothat the current will be broken and the dial-hand stopped, although thecurrent in As line may keep the contact-piece 125 bridged for a shorttime longer. When the central selecting device is swung for the purposeabove described, the pivoted finger 104 rides over the flange 121 whichdepresses the spring-arm 99 and breaks the bridge between theconducting-rings 100 at the zeropoint; otherwise the dial hand would notstop at D, but would come entirely around to zero. It will also beremembered that when the dial-hand passed D the spring-arm at that pointwas pressed inwardly until the squared part of the key 102 engaged inthe slot in the spring-arm and held it depressed after the dial-handmoved on. I will assume now that D does not answer As call, in whichcase it is necessary to return his line to zero from the centralstation. I/Vhen this line was turned to D, the current was broken fromthe central station and the standard 107 rose into vertical position, aspreviously described, with the dialhand at D and the conducting-rings100 bridged at zero. When the central operator becomes satisfied that Dwill not answer his call, she again swings the standard 107 as beforeandat the same time depresses the pivoted finger 104 so as to bring itbelow the flange 121. The arm 99 is not depressed, therefore, as waspreviously the case, and as soon as the circuit is established at thecontacts 132, 133, 134, and 135 the current will again flow from thecentral battery through Ds line and will continue until the dial-hand 96reaches Zero, when it will depress the special arm 99 and break thecircuit, after which the standard 107 and finger 104 return to theirnormal positions.

In case A and D, for example, on the same line wish to converse it isonly necessary for one of them to take off his receiver and press his ADkey, when the selecting devices on that line will turn to'the ADposition and place those two parties in talking-circuit, it beingremembered that they each have a key 47 at this point. In passingaroundto theAD key the dial-hands passed and depressed all the spring'arms 41at the A, B, C, and I D positions. These arms have no radial keys 520 tohold them when depressed; but they are prevented from springing out tobridge the conducting-rings 40 after the dialhand has passed by thehooks 58. When the dial-hands return to zero, these hooks are pressedback to release the spring-arms by the cams on the plunger-s of thezero-keys. The cams 66 on these plungers simultaneously swing thelocking-rings 83, and as soon as the current is broken at 40 and 62 themagnets 33 will be deenergized, which will permit the locking-rings 90to be moved by the springs 82 to unlock all the receiver-hooks and keys520 on the line.

Having thus described my invention, what I claim as new, and desire'tosecure by Letters Patent, is-

1. In a telephone system, a main line, a plurality of telephones on saidline,said telephones having receiver-hooks, a selecting device connectedwith each telephone, said selecting devices being adapted to operatesimultaneously and synchronously, a rod connecting each telephone-hookand its selecting device, a perforated plate mounted for movement insaid selecting device, the perforation being normally opposite the saidrod, and means for shifting said plate to cause it to engage the rod andhold it so that the telephone-hook cannot be moved.

2. In a telephone system, a main line, a plu rality oi telephones onsaid line,said telephones having receiver-hooks, a selecting deviceconnected with each telephone, said selecting devices being adapted tooperate simultaneously and synchronously, and mechanism at eachselecting device that is operated when a receiver-hook is lifted toautomatically lock all the hooks of the other receivers against release.

3. In a telephone system, a main line, a plurality of telephones on saidline, said telephones having receiver-hooks, a selecting deviceconnected with each telephone, said selecting devices being adapted tooperate simultaneously and synchronously, a dial-hand on eachselectingdevice,a rod connecting each telephonehook and its selectingdevice, a plate mounted for movement in each selecting device, saidplates having perforations opposite the rods when the dial-hands are innormal position, means for causing the plates to shift to lock the rodsand the hooks when the dial-hands move from normal position, keysprojecting into the'path of the dial-hand to be depressed by the latter,and means on said keys for shifting the said plates to unlock the rods.

4. In a telephone system, a main line, a plurality of telephones on saidline,said telephones having receiver-hooks, a selecting device connectedwith each telephone, a dial-hand on each selecting device, a locking-rodconnected with each receiver-hook and extending to the correspondingselecting device, plates in the selecting devices for locking the saidrods, means for shifting the plates to their unlocking position whilethe dial hands are in zero position, means for shifting said plates totheir locking position when the dial-hands move from their zeroposition, keys projecting into the path of the dial-hands to bedepressed by the latter, and means on said keys for shifting the platesto their unlocking positions, the arrangement of the keys being suchthat but one key will be depressed at a time, and only that telephonehaving that key will have its receiver-hook unlocked.

5. In a telephone system, a main line, telephones on said line, acentral station from which said line extends, a selecting device at thecentral station that is normally disconnected from said line, means forplacing said selecting device in circuit with said line, means in saidselector for automatically breaking said circuit after a predeterminedtime, selecting devices at each of the said telephones, said devicesbeing in the same circuit With the selecting device at central, keys onsaid devices,

means for locking the keys of all the telephones that are on the lineexcept those at one telephone, and means for sounding the signal at thattelephone.

6. In a telephone system, a central station, a main line extending fromsaid station, telephones on said line, a movable selecting device at thecentral station, selecting devices at the telephones, a cable adapted toconnect the movable selecting device with the main line, a source ofelectric power at the central station, contact-points that are closedwhen the central selecting device is moved to connect the said devicewith the main line, and contacts in the said device that may be manuallyclosed to establish a circuit from the said source of power through thecable and the selecting devices to set them to a predetermined position.

7. In a telephone system, a central station, a main line extending fromsaid station, telephones on said line, amovable selecting device at thecentral station said device having keys for controlling electriccontacts therein, selecting devices at the said telephones; a cableadapted to connect the central selecting device with the main line, asource of electric power at the central station, contact-points that areclosed when the central selecting device is moved to connect the saiddevice with the main line, contacts in the said device that are closedby the depression of the keys to establish a circuit from said source ofpower through the cable and the selecting devices to set them to apredetermined position.

8. In a telephone system, a central station, a plurality of main linesextending from said station, telephones on each of said lines, a cableat the central station through which a pair of said lines may beconnected, said cable being separable intermediate its length, a movableselecting device at the central station and a selecting device at eachof the said telephones, a source of electric power at the centralstation, means whereby the movement of the central selecting deviceopens the cable and places the source of power in circuit with one ofthe lines, and means in the said device for completing said circuit sothat all the selecting devices will be operated for a predeterminedtime.

9: In a telephone system, acentral station, a plurality of main linesextending from said station, telephones on each of said lines, a cableat the central station through which two of said lines may be connected,said cable being separable intermediate its length, a movable selectingdevice at the central station and a selecting device at each of saidtelephones, a source of electric power at the central station, meanswhereby the movement of the central selecting device opens the cable andconnects the source of power therethrough with one of the lines, meansin the said device f'orcompleting said circuit so that the selectingdevices at central and on the connected line will be operated for apredetermined time, means for holding the central selecting device inits moved position, and means for releasing the same so that it may berestored as the devices come to rest.

10. In a telephone system, a central station, a plurality of main linesextending from the said station, telephones on each of the said lines, acable at'the central station through which two of said lines may beconnected, said cable being separableintermediate its length,a movableselecting device at the central station, said device being mounted on apivoted standard, a selecting device at each of said telephones, asource of electric power at the central station, a pin projecting fromthe pivoted standard, said pin opening the said cable as the standard isswung, contacts on said standard that puts the source of power incircuit with one part of the cable and with the line connected therewithas the standard is swung,

means in the central selecting device for com pleting said circuit sothat the selecting devices at central and on the connected line will beoperated for a predetermined time, means for holding the pivoted arm inits moved po sition, and means for releasing the same so that it may berestored as the devices come to rest.

11. In a telephone system, a central station, a plurality of main linesextending from said station, telephones on each of said lines, a cableat the central station through which two of said lines may be connected,said cable being composed at one part intermediate its length of twopairs of normally contacting springs 118, a movable selecting device atthe central station,said device being mounted on a pivoted standard, aselecting device at each of said telephones, a source of electric powerat the central station, a pin projecting from the pivoted standardbetween the contacting springs 118 and contacts on said standard so thatas the standard is swung on its pivot the springs will be pressed apartand the source of power connected with one part of the cable and throughit with one of the main lines, means in the central selecting device forclosing the circuit from the source of power and means for automaticallybreaking the same after a predetermined time whereby all the selectingdevices are brought to rest.

12. In a telephone system, a central station, a plurality of main linesextending from said station, telephones on each of said lines, a cableat the central station through which two of said lines may be connected,said cable being composed at one part intermediate its length of twopairs of contacting springs 118, a selecting device at the centralstation, said device being mounted on a pivoted standard, a selectingdevice at each of said telephones, a source of electric power, as abattery at the central station, a pin projecting from the pivotedstandard between the contacting springs 118, and contacts on saidstandard, so that as the standard is swung on its pivot the springs willbe pressed apart and the battery connected with one part of the cableand through it with one of the main lines, means in the centralselecting device for closing the circuit from the source of power, meansfor automatically breaking the same after a predetermined time, asolenoid and plunger for holding the pivoted standard in one positionand a spring for drawing back the plunger when the current through thesolenoid is broken so that the standard may return to its normalposition.

13. In a telephone system, a central station, a party-line leading tosaid station, telephones on said line, a selecting device at the centralstation and at each of the said telephones, connections whereby the saidcentral selecting device may signal and place one of the said telephonesin condition for use to the exclusion of all other telephones on theline, con nections whereby the said telephone that has been signaled andits selecting device will, if the call has been answered and thereceiver removed from the hook, automatically return all the selectingdevices to Zero, and means for restoring the first-mentioned connectionsfrom the central selecting device to return the said devices to zero ifthe party signaled does not answer.

14:. In a telephone system, a main line, telephones on said line,selecting devices for controlling said telephones, an electromagnet ateach selecting device, and means controlled by a part of the telephoneproper that is operating for keeping the other telephones of]? thetalking-circuit while the selecting devices are operating, said meansbeing controlled by the said electromagnets.

15. In a telephone system, a central station, a main line leading fromsaid station, telephones on said line said telephones havingreceiver-hooks, a selecting device at the central station that isadapted to be connected with the said line, means within the saidselecting device for closing a circuit through the said main line andfor automatically breaking it after a predetermined time, a selectingdevice for each telephone, said devices being in the circuit with thedevice at the central station and operating synchronously therewith, anelectromagnet at each of the telephone-selecting devices that releasesthe operating mechanisms of said devices, means for locking thetelephone hooks, and armatures connected with said means, said armaturesbeing operated by the said electromagnets.

16. In a telephone system, a main line, telephones on said line, saidtelephones having receiver-hooks, a selecting device for each telephone, an electromagnet in each selecting device, a zero-key for each ofsaid devices, and double means for locking the receiver-hooks, one ofsaid means being controlled by the electromagnets and the other by thezero-keys.

17. In a telephone system, a mainline, telephones on said line, saidtelephones having receiverhooks, a selecting device connected with eachtelephone, said selecting device having Zero and bell-circuit keys, anelectromagnet in each selecting device for controlling the same, alocking-rod connecting each telephone-hook with its selecting device, alocking-plate in the selecting device for locking the said rod, saidplate being under the control of the zero and bellcircuit keys, and asecond locking-plate for said rod that is under the control of theelectromagnet, for the purpose specified.

- 18. In a telephone system, a main line, telephones on said line saidtelephones having receiver-hooks, mechanism at each telephone that isoperated when a receiver is lifted from its hook to automatically keepall the telephones on the line out of the talking-circuit except the onewhose receiver has been lifted, a return-to-Zero circuit having a set ofcontacts at the telephone whose receiver has been lifted, and means forseparating the contacts and thus breaking the return-to-zero circuit,said means being controlled by the receiver-hook.

19. In a telephone system, a main line, telephones on said line, aselecting device at each telephone whereby one telephone may be placedin the talking-circuit to the exclusion of all other telephones on theline, a returnto-zero circuit having a set of contacts below thereceiver-hook, a plate adapted to separate the contacts, and aspring-pressed lever pivoted to the telephone-casing below the outer endof the hook and normally tending to cause the plate to separate thecontacts, said lever projecting into a position to be depressed by thereceiver as it hangs on its hook so that the contacts may come together.

In testimony whereof I afliX my signature in the presence of twowitnesses.

ALBERT J. SPRINGBORN.

\Vitnesses S. E. FoU'rs, BRENNAN WEsT.

